In electric motors of this type, such as four-pole motors incorporated in starters for motor vehicle combustion engines, an effort is made to assemble only two brushes and two brush holders placed 90.degree. in relation to one another, a solution that is more economical than another known solution which consists of providing four brushes and four brush holders. However, a problem arises during assembly, particularly when two brush holders placed at 90.degree. are mounted on a support piece in the form of a washer independent of the flange constituting the cover and bearing of the electric motor. If this arrangement of the brush holders as an independent part makes it possible to make the electric connection of the brushes under good accessibility conditions, on the other hand, these brushes, under the pressure of the springs that act on them, cause the support washer to be thrown off center in relation to the commutator, thus making later mounting of the flange, which forms the motor cover and shaft bearing, more difficult.
In numerous cases, this difficulty of mounting the flange resulting from this off-centering leads to abandoning the solution of the support washer to hold the brush holders when they are two and placed at 90.degree., and this design solution is therefore often limited to four-brush rotating machines only.